The present invention relates generally to the field of graphic computer input devices. More specifically, the present invention relates to a passive paint brush stylus formed of a solid piece of a resiliently compliant non-conductive material that interacts with a touch screen display of a computer painting system to provide a computer input system that more closely replicates the actions of conventional painting.
The most popular input devices for computers are the keyboard and mouse. In the field of graphic computer input devices, however, the use of alternative input devices is well known. There are numerous systems that use a passive stylus or pen in connection with a touch screen or digitizing pad. These types of input systems are particularly popular as a way of recognizing handwriting input. A recent example of these types of input systems can be found in U.S. Pat. No. 5,990,875. The passive stylus for these types of input systems is a rigid pen-like device with a somewhat rounded point at the tip of the stylus. This is because the goal of these input systems is to accurately digitize and discriminate the particular spot being indicated by the tip of the stylus and to allow for easy movement of the stylus across the screen or input pad without the stylus being so sharp as to damage the screen or input pad. In one of the more popular applications as an input device for recognizing handwriting for a personal digital assistants (PDAs), it is also important that the stylus be relatively inexpensive so that it can be easily replaced if lost.
While this type of rigid passive stylus is well suited for point recognition applications such as handwriting recognition, it is not well suited to replicating the techniques of conventional painting. In a conventional painting process, the bristles in the tip of a paint brush carry the paint across a surface and create various marks depending upon the size of the brush, the pressure and speed with which the brush is moved across the surface and the angular orientation of the brush relative to the surface. Alternative paint tools such as spatulas or palette knives carry the paint on a surface of the flat tip of the tool that is then spread across the surface in a manner similar to a bristle paint brush; however, the marks made by a spatula or knife on the surface are generally distinct from those created by a conventional bristle paint brush. A silicone paint brush tool that can more closely replicate the manner and strokes as applied by a conventional bristle paint brush is described in U.S. Pat. No. 5,542,144. In contrast to the point oriented nature of a rigid passive stylus, each of these painting tools distributes paint on the surface being painted in a spreading fashion that results in variable width, thickness and density of paint being applied to the surface. As a result, it is difficult to replicate the performance of such painting tools in the context of a graphic computer input device using a rigid passive stylus.
A number of systems have been developed that utilize an active stylus as part of a graphic computer input system in an effort to more closely replicate the results of conventional painting techniques. In contrast to the passive stylus, an active stylus has some electronic or optical components in the stylus that interact with the computer and input screen as part of the graphic input system. For example, U.S. Pat. Nos. 5,420,607 and 5,646,650 describe an electronic paintbrush and color palette that allow a user to generate images on a CRT screen in a manner that imitates conventional painting by using an electronic stylus with fiber optic bristles embedded in the tip of the stylus. A microprocessor in the stylus scans the CRT screen to determine position, angular orientation and pressure of the stylus relative to the screen and communicates this information to the computer controlling the CRT screen to control the generation of images on the screen. Other examples of input systems that use an active or intelligent stylus coupled to a computer are described in U.S. Pat. Nos. 5,155,813, 5,343,220, 5,528,266, 5,557,301, 5,581,052, 5,635,683, 5,959,616 and 5,977,958. Examples of a pressure-sensitive stylus or pen connected to a computerized graphic system that mixes or combines certain predetermined colors, such as the primary colors, on an electronic palette arrangement are described in U.S. Pat. Nos. 4,524,421 and 5,343,220. U.S. Pat. No. 5,861,878 describes a graphic input system that utilizes a mouse input, but represents a graphically modeled painting brush with elastic bristles on the display screen. The obvious problem with such active stylus systems is that the stylus must be relatively complicated and must be coupled in some manner to the computer and display screen. This complexity increases the cost of the system and can interfere with the ability of the system to emulate conventional painting techniques.
A few patents have attempted to use a passive stylus in a manner that imitates conventional painting techniques, rather than as a point entry device for handwriting recognition or the like. U.S. Pat. No. 5,434,959 describes a system for generating variable width lines in which the pressure exerted by a rigid passive stylus or pen on a pressure sensitive tablet and, specifically, for addressing the problem of how to maintain the width of a line as the pen is removed from the tablet. U.S. Pat. No. 5,488,204 describes a paint brush stylus for a capacitive touch sensor pad. The paint brush stylus is comprised of conductive fibers held together at the tip of the stylus like a conventional paint brush. This patent teaches that neither resistive nor acoustic wave touch screens are suitable for simulating conventional painting techniques. Instead, the conductive fibers of the paint brush stylus interact with a capacitive touch-sensor pad to simulate paint-like strokes on a display associated with the capacitive touch-sensor pad.
Despite the various attempts to replicate the process of conventional painting techniques for a computer graphic input system, a simple, economical and accurate representation of conventional painting techniques has yet to be developed for a computer graphic input system.
The present invention is a computer painting system in which a graphic computer system has at least one touch screen apparatus and at least one display. A stylus having a tip formed of a solid piece of a resiliently compliant non-conductive material is used to apply variable pressure on the surface of the touch screen apparatus. Software executing on the computer system interprets the variable pressure made on the touch screen apparatus and generates corresponding graphic images on the display. Preferably, the tip of the stylus is formed of a silicone material that allows the tip to easily move across the touch screen apparatus in a way that simulates a conventional painting brush stroke but without leaving a buildup of material on the touch screen apparatus. In one embodiment, the touch screen apparatus and the display are incorporated together in the same device. In another embodiment, the touch screen apparatus is a palette physically separate from the display and operably connected to the computer system. Preferably, the touch screen apparatus is a surface acoustic wave touch screen device.
In a preferred embodiment, the palette is provided with a spectral color wheel and a plurality of selected color pads and mixed color pads representing available colors to be applied, as well as buttons for controlling applied color attributes such as color consistency, texture, mixing, loading, translucence and blendability. In another embodiment, a scanner is utilized to generate input color data for the palette. Multiple different renditions of the palette may be cataloged and saved for subsequent use to allow a user to build up a repertoire of specifically chosen palettes.